Fuel supply apparatus

ABSTRACT

A fuel feed pump according to the present invention improves its pump performance by making smaller side clearances in an axial direction at both sides of a pump element PE.  
     Multiple through-holes passing through in an axial direction are respectively formed at top portions of cogs of the outer rotor and the inner rotor, which form a pump element of a feed pump. Accordingly, pressures in the thrust direction at both axial sides of the rotors can be equalized, since the side clearance formed at both axial sides of the rotors are communicated with each other. As a result, since the rotors can be floated, without contacting with the pump cover and the pump plate, the abnormal wear and seizures can be suppressed, even when side clearance between the pump cover and the pump element is made smaller.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based on Japanese Patent Application Nos. 2003-159280 filed on Jun. 4, 2003 and 2004-125490 filed on Apr. 21, 2004, the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to a fuel supply apparatus for an internal combustion engine, more particularly to a rotary pump to be used for a fuel injection system for supplying fuel to a diesel engine.

BACKGROUND OF THE INVENTION

[0003] As one of prior art fuel injection pump, for example shown in U.S. Patent Application Publication No. US 2003/0044288 A1, it is known to us that the fuel injection pump is provided with a feed pump for drawing fuel from a fuel tank and feeding the fuel to a main pump of the fuel injection pump.

[0004] As shown in FIG. 6, the feed pump comprises a pump element 110 to be driven by a cam shaft 100 of a main pump, a pump cover 120 for forming a rotor chamber and housing therein the pump element 110, and a pump plate 130 for closing an opening side of the rotor chamber in a liquid-sealing manner in combination with the pump cover 120, wherein the pump cover 120 is screwed to a side surface of a pump housing 140.

[0005] Furthermore, as shown in FIG. 7, the pump element 110 is a trochoid type comprising an outer rotor 111 having inner cogs and an inner rotor 112 disposed inside of the outer rotor and having outer cogs, wherein the number of cogs of the outer rotor 111 is larger than that of the inner rotor 112 by one cog, and wherein a rotational center 0 a of the outer rotor 111 is eccentric from that 0 i of the inner rotor 112. As a result, when the inner rotor 112 is driven by the cam shaft 100 and rotated, the outer rotor 111 is also rotated in conjunction with the inner rotor 112, so that a volume of a working chamber formed by adjacent cogs will be gradually changed to draw fuel from a fuel tank and pumps out the fuel to the main pump.

[0006] In the above described feed pump, as shown in FIG. 6, a side clearance between the pump cover 120 and the pump element 110 is made smaller to minimize amount of fuel leakage and to increase a fuel feed efficiency. If, however, the side clearance were made too small, there would occur a problem of an abnormal wear, seizure or the like, because variations of parts in manufacturing process may not be absorbed.

SUMMARY OF THE INVENTION

[0007] The present invention is made in view of the above problems, and it is an object of the present invention to provide a fuel supply apparatus having a rotary pump which improves a pump performance by making much smaller the side clearance in an axial direction at both sides of the pump element without causing metal contact between the pump element and the counterpart.

[0008] According to one of features of the present invention, a fuel supply apparatus comprises a rotary pump having a pumping chamber, the volume of which varies in conjunction with a rotation of a rotor, pressurizing the fuel sucked into the pumping chamber and discharging the pressurized fuel. The rotary pump is characterized in that, multiple through-holes are formed in a rotor, wherein the through-holes pass through in the rotor in an axial direction, and side clearances formed at both sides of the rotor are communicated with each other by those through-holes.

[0009] According to the above structure, pressures (thrust pressures) on both sides of the rotor in the axial direction are equalized, since the side clearances formed at both sides of the rotor are communicated with each other through those multiple through-holes formed in the rotor. As a result, uniform side clearances on both sides of the rotor can be attained. In other words, it has become possible to float the rotor. Accordingly, the fuel feed efficiency can be increased by making much smaller the side clearance formed at both sides of the rotor in its axial direction, and the problems of the abnormal wear, seizures and the like can be suppressed because metal contacts between the rotor forming the side clearances and other parts can be suppressed.

[0010] According to another feature of the invention, the multiple through-holes are formed at an equal distance in a circumferential direction of the rotor.

[0011] According to such a structure, since the pressures (thrust pressures) on both sides of the rotor are equalized through those multiple through-holes at those points of the equal distance in the circumferential direction of the rotor, uniform side clearances can be obtained on both sides of the rotor at almost all circumferential points of the rotor. Accordingly, the fuel feed efficiency can be increased by making the side clearances much smaller, and the problems of the abnormal wear, seizures and the like can be suppressed because metal contacts between the rotor and other parts can be suppressed.

[0012] According to a further feature of the invention, the rotary pump is a trochoid type pump comprising an outer rotor having inner cogs and inner rotor disposed inside of the outer rotor and having outer cogs, wherein the through-holes are formed at top portions or bottom portions of the cogs.

[0013] Because of the through-holes formed in the inner rotor, which is driven by a camshaft, the inner rotor can be floated. As a result, metal contacts between the inner rotor and other parts are suppressed during the rotation of the inner rotor, and thereby the problems of the abnormal wear, seizures and the like can be suppressed.

[0014] According to still further feature of the invention, the rotary pump is provided with the through-holes at every top portion or bottom portion of the cogs.

[0015] In this case, the pressures in the thrust direction can be equalized at every top portion or bottom portion of the cogs of the inner rotor, the inner rotor can be much more surely floated to suppress the metal contacts between the inner rotor and the other parts.

[0016] According to a further feature of the invention, an outer rotor of the rotary pump is provided with multiple through-holes, which pass through in the axial direction, at top portions or bottom portions of the cogs, wherein the multiple through-holes are arranged at an equal distance in a circumferential direction of the outer rotor.

[0017] Since the through-holes are formed in the outer rotor in addition to the through-holes in the inner rotor, thrust pressures to the outer rotor can be likewise equalized. As a result, the outer rotor can be positively floated together with the inner rotor.

[0018] According to a further feature of the present invention, the rotary pump is used as a feed pump of a fuel injection pump for diesel engines, wherein the feed pump is formed with a circular rotor chamber and comprises a pump cover for housing the pump element of the inner and the outer rotors in the rotor chamber, and a pump plate for closing an open end of the rotor chamber in a liquid-sealing manner together with the pump cover. The pump plate is formed with fuel ports to be communicated to the rotor chamber, and the pump cover is screwed to a side surface of a housing of the fuel injection pump, so that the pump plate is pressed against the side surface.

[0019] According to the above structure, the side clearance between the pump element and the pump cover as well as the side clearance between the pump element and the pump plate can be made smaller to increase the fuel feed efficiency and thereby increase a pump performance as the feed pump.

[0020] According to a further feature of the invention, the rotary pump is a vane type pump comprising a rotor formed with vane grooves and vanes movably inserted into the vane grooves.

[0021] In the vane type pump, since the rotor having vanes is driven by a cam shaft and is rotated, the rotor can be floated by equalizing thrust pressures with multiple through-holes formed in the rotor. As a result, the metal contacts between the rotor and the other parts can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

[0023]FIG. 1 is a cross-sectional view of a feed pump according to a first embodiment of the present invention;

[0024]FIG. 2 is a front view of a pump element of the feed pump shown in FIG. 1;

[0025]FIG. 3 is a cross-sectional view of a fuel injection pump to which the feed pump of the present invention is applied;

[0026]FIG. 4 is a front view of a pump element according to a second embodiment of the present invention;

[0027]FIG. 5 is a front view of a pump rotor according to a third embodiment of the present invention;

[0028]FIG. 6 is a cross-sectional view of a prior art feed pump; and

[0029]FIG. 7 is a front view of a pump element of the feed pump shown in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

[0030] The present invention will be explained below with reference to the embodiments.

[0031] In the first embodiment, an embodiment is explained in which a fuel supply apparatus of the invention is used in a fuel injection pump of a common rail fuel injection system for diesel engines.

[0032]FIG. 1 is a cross-sectional view of a feed pump, FIG. 2 is a front view of a pump element, and FIG. 3 is a cross-sectional view of a fuel injection pump.

[0033] As shown in FIG. 3, the fuel injection pump 1 is provided with a main pump 2 for pressurizing and pumping out fuel and a feed pump 3 (See FIG. 1) for drawing the fuel from a fuel tank (not shown) and feeding the fuel to the main pump 2.

[0034] The main pump 2 comprises a cam shaft 4 to be rotated being driven by a diesel engine (not shown), a pump housing 5 for rotationally supporting the cam shaft 4, a plunger 7 being driven by the cam shaft 4 for reciprocally moving in a cylinder 6, and so on.

[0035] A cam 8 which has a circular cross-sectional configuration is fixed to the cam shaft 4, wherein a rotational center thereof is eccentric to that of the cam shaft. A cam ring 10 is rotationally supported at an outer periphery of the cam 8 over a bush 9. A pair of flat surfaces are formed in the cam ring 10, wherein the flat surfaces are opposing to each other in a radial direction of the cam 8.

[0036] A pair of cylinder heads 11 is assembled to the pump housing 5 in a liquid-sealing manner, wherein the cylinder heads 11 are opposing to each other in the radial direction of the cam shaft 4.

[0037] The cylinder head 11 is formed with a cylinder 6, into which the plunger 7 is inserted, a pump-out port 12 to be communicated with the cylinder 6, and so on. A check valve 13 is assembled to the cylinder head at an opposite side of the cylinder 6. A pipe joint 15 is screwed into the cylinder head at an outlet side of the pump-out port 12 for connecting to a fuel pipe 14.

[0038] The check valve 13 is disposed between a fuel passage (not shown) to be communicated with a feed pump and the cylinder 6. The check valve 13 will be opened during a suction stroke at which the plunger 7 will be downwardly moved in the cylinder 6 (inwardly moved), to introduce fuel fed from the feed pump 3 into the inside of the cylinder 6, whereas the check valve 13 will be closed during a pumping out stroke at which the plunger 7 will be upwardly moved in the cylinder 6 (outwardly moved) so that the fuel introduced into the cylinder 6 is prevented from flowing back to the feed pump 3.

[0039] The pump-out port 12 is formed with a small diameter port and a large diameter port. A seat surface of a circular conic is formed between the small and large diameter ports (See FIG. 3). A ball valve 17 is disposed in the pump-out port 12 and is urged by a spring 16 towards the seat surface, so that the small and large diameter ports are blocked by this ball valve 17.

[0040] The ball valve 17 will be lifted from the seat surface when a pressure of fuel, which is pressurized by the plunger 7 during the pumping out stroke, becomes higher than the urging force of the spring 16, and thereby the small and large diameter ports are communicated with each other.

[0041] The plunger 7 has a plunger head 7 a at its inner side end and the plunger head 7 a is urged by a spring 18 and pressed against an outer surface (flat surface) of the cam ring 10. When the rotation of the cam shaft 4 is transmitted to the cam ring 10 via the cam 8, the cam ring 10 moves with an orbital motion along its orbit which is displaced from the rotational center of the cam shaft 4 by a certain distance, while the cam ring 10 is keeping its orientation (The cam ring 10 is not rotated on its axis and on an axis of the cam 8). As a result, the plunger 7 pressed against the flat surface of the cam ring 10 is reciprocally moved in the cylinder 6.

[0042] The feed pump 3 comprises a pump element PE, a pump cover 19 and a pump plate 20, as explained below. The feed pump 3 is fixed to a side surface of the pump housing 5 by bolts 21, as shown in FIG. 3.

[0043] The pump element PE is a well known trochoid type pump, comprising an outer rotor 22 having inner cogs and an inner rotor 23 disposed inside of the outer rotor 22 and having outer cogs, wherein the inner rotor is connected to the cam shaft 4 via a key so that the inner rotor will be rotated by the cam shaft 4.

[0044] The outer rotor 22 has cogs, the number of which is larger than that of the inner rotor 23 by one cog, and the rotational center 0 a of the outer rotor 22 is eccentrically displaced from the rotational center 0 i of the inner rotor 23 (See FIG. 2). Accordingly, when the inner rotor 23 is rotated by the cam shaft 4, the outer rotor 22 is rotated in conjunction with the inner rotor 23, so that the volume of working chambers formed by the cogs will be changed to pump out the fuel drawn from the fuel tank to the main pump 2.

[0045] As shown in FIG. 2, through-holes 22 a and 23 a, which pass through the outer and inner rotors 22 and 23 in an axial direction, are respectively formed in the outer rotor 22 and the inner rotor 23. There are provided with multiple through-holes 22 a and 23 a in the outer and inner rotors 22 and 23, and those through-holes are formed at an equal distance in a circumferential direction (more exactly, at every cog top portion of the outer and inner rotors 22 and 23).

[0046] The pump cover 19 is formed with a circular rotor chamber 19 a for housing therein the pump element PE, as shown in FIG. 1. An inner diameter of the rotor chamber 19 a is made slightly larger than an outer diameter of the pump element PE (namely, an outer diameter of the outer rotor 23), so that the outer rotor 23 may be rotated therein. A width of the rotor chamber 19 a is made slightly larger than a width of the pump element PE (a thickness in a longitudinal direction), so that side clearances of a certain distance between the pump element PE and inner surfaces of the pump chamber are kept.

[0047] The pump plate 20 is assembled to the pump cover 19 in a liquid-sealing manner to close an opening of the rotor chamber 19 a. The pump plate 20 is formed with a center bore, through which the cam shaft 4 passes, and fuel ports 20 a (an inlet port and an outlet port) around the center bore (See FIG. 1). The fuel ports 20 a are communicated to the working chambers 24 formed between the outer rotor 22 and the inner rotor 23.

[0048] An operation of the above first embodiment will be explained. In the above feed pump 3, the multiple through-holes 22 a and 23 a are respectively formed in the outer and inner rotors 22 and 23 and furthermore those multiple through-holes 22 a and 23 a are arranged at equal distance in the circumferential direction of the rotors 22 and 23. Since the side clearances formed on the both sides of the rotors 22 and 23 in the axial direction are communicated with each other through those multiple through-holes 22 a and 23 a, the pressures in the thrust direction at the both sides of the rotors 22 and 23 will be equalized. As a result, uniform side clearances can be obtained at both sides of the rotors 22 and 23.

[0049] According to the above structure, the outer and inner rotors 22 and 23 can be floated without contacting with the pump cover 19 and the pump plate 20. In particular, since the through-holes 23 a are formed at every cog top portions of the inner rotor 23, which correspond to an outer periphery of the inner rotor, an inclination of the inner rotor 23 can be effectively suppressed and thereby the uniform side clearances at both of the longitudinal sides along the peripheries of the inner rotor 23 can be obtained.

[0050] Accordingly, the problems of the abnormal wear and seizures and the like can be suppressed by preventing the metal contacts between the pump element PE and the pump cover 19 and the pump plate 20, to finally increase the performance of the feed pump 3, even when the side clearances between the pump element PE and the pump cover 19 are made smaller to increase the fuel feed efficiency.

[0051] In the above first embodiment, the through-holes 22 a and 23 a are formed in the both outer and inner rotors 22 and 23. It is, however, possible to obtain a sufficient effect (suppress of the abnormal wear and seizures, or the like), when the through-holes 23 a are formed only in the inner rotor 23 which is directly driven by the cam shaft 4.

Second Embodiment

[0052]FIG. 4 is a front view of pump element PE according to a second embodiment.

[0053] In the first embodiment, the multiple through-holes 22 a and 23 a are formed in the outer and inner rotors 22 and 23 at equal distance in the circumferential direction. It is, however, not necessary to arrange the through-holes at equal distance. As shown in FIG. 4, the through-holes 23 a can be formed in the inner rotor 23 at non-equivalent distances in the circumferential direction. Although only the through-holes for the inner rotor 23 are shown in FIG. 4, the through-holes 22 a can be formed in the outer rotor 22 at non-equivalent distances in the circumferential direction, as in the same manner for the inner rotor 23.

Third Embodiment

[0054]FIG. 5 is a front view of a rotor 25 according to a third embodiment.

[0055] The third embodiment is an embodiment in which the present invention of the rotary pump is applied to a vane type pump.

[0056] The vane type pump has, as shown in FIG. 5, a rotor 25 formed with multiple vane grooves 25 a at its outer periphery at equal distance in the circumferential direction, and vanes 26 respectively and movably inserted into the vane grooves 25 a.

[0057] When the multiple through-holes 25 b are formed in the rotor 25 and the rotor 25 is floated, as in the same manner to the first embodiment, metal contacts with other parts can be prevented and thereby the problems of the abnormal wear and seizures and the like can be suppressed.

[0058] In this embodiment as shown in FIG. 5, the through-holes 25 b are formed at both sides to the respective vanes 26 and the circumferential distance of the through-holes 25 b between the respective vanes 26 is arranged to be equal to each other. However, the circumferential distance of the through-holes 25 b is not necessary to be equal but to be non-equivalent.

Other Embodiments

[0059] The above embodiments are explained as those embodiments in which the fuel supply apparatus of the invention is used in the fuel injection pump of the common rail fuel injection system for diesel engines. The present invention is not limited to these embodiments, and the present invention can be used for a fuel pump for a gasoline engine. 

What is claimed is:
 1. A fuel supply apparatus comprising: a rotary pump having a rotor and a pumping chamber, volume of the pumping chamber being varied in conjunction with rotation of the rotor, and for pressurizing fuel sucked into the pumping chamber and discharging the pressurized fuel, wherein multiple through-holes are formed in the rotor in its axial direction, and side clearances formed at both sides of the rotor are communicated with each other though those through-holes.
 2. A fuel supply apparatus according to claim 1, wherein the multiple through-holes are formed at an equal distance in a circumferential direction of the rotor.
 3. A fuel supply apparatus according to claim 1, wherein the rotary pump is a trochoid type pump comprising an outer rotor having inner cogs and an inner rotor disposed inside of the outer rotor and having outer cogs, wherein the through-holes are formed at top portions or bottom portions of the cogs.
 4. A fuel supply apparatus according to claim 3, wherein the rotary pump is provided with the through-holes at every top portion or bottom portion of the cogs.
 5. A fuel supply apparatus according to claim 3, wherein an outer rotor of the rotary pump is provided with multiple through-holes, which pass through in the axial direction, at top portions or bottom portions of the cogs.
 6. A fuel supply apparatus according to one of claim 3, wherein the fuel supply apparatus is a fuel injection pump for a diesel engine for which the rotary pump is used as a feed pump, wherein the feed pump comprises: a circular rotor chamber; a pump cover for housing a pump element of the inner and the outer rotors in the rotor chamber; and a pump plate for closing an open end of the rotor chamber in a liquid-sealing manner together with the pump cover, wherein the pump plate is formed with fuel ports to be communicated to the rotor chamber, and the pump cover is screwed to a side surface of a housing of the fuel injection pump, so that the pump plate is pressed against the side surface.
 7. A fuel supply apparatus according to claim 1, wherein the rotary pump is a vane type pump comprising a rotor formed with vane grooves and vanes movably inserted into the vane grooves.
 8. A fuel supply apparatus for an internal combustion engine comprising: a main pump for supplying a high pressure fuel to the engine; and a feed pump fixed to the main pump for feeding fuel from a fuel tank to the main pump, wherein the feed pump including: a pump housing forming a pumping chamber; and a pump rotor operatively connected to the main pump and rotationally supported in the pumping chamber, wherein multiple through-holes are formed in the rotor so that side clearances between the pump housing and both side surfaces of the rotor are communicated with each other.
 9. A fuel supply apparatus according to claim 8, wherein the multiple through-holes are formed in the rotor at an equal distance in a circumferential direction.
 10. A fuel supply apparatus according to claim 8, wherein the feed pump is of a trochoid type pump comprising: an outer rotor rotationally supported in the pump housing and having inner cogs; and an inner rotor disposed inside of the outer rotor and having outer cogs, wherein the multiple through-holes are formed at the respective cogs. 